AlgebraMediumMissing x-coordinate of a point on a line through two points
Algebra practice question
In the xy-plane, the line through the points (−2, 5) and (4, −1) also passes through the point (k, 3). What is the value of k?
Answer: 0
Slope = (−1 − 5)/(4 − (−2)) = −6/6 = −1. Using (4, −1): y = −x + 3. For y = 3: 3 = −k + 3, so k = 0.
Common wrong answers
- If you answered 3
- 3 is the y-intercept of the line, and also the y-coordinate given; k is the x-coordinate where y = 3.
- If you answered 6
- 6 is the run between the two given points, not k.
- If you answered -3
- −3 comes from a sign slip in y = −x + 3.
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